While the availability of resources to produce energy is a worrying subject, and the expression "renewable energies" is on everyone's lips, little is said about marine energy flows. However, they are a promising avenue in the exploration of decarbonized and renewable energy, available throughout the planet. Explanations.
Marine energy is a renewable energy. A renewable energy is called this because it is considered infinite, unlike "finite" resources such as oil, coal or gas: when there is no more, there will be no more, unlike wind for example. So we knew about wind turbines that produce electricity with the wind, solar panels with the sun's rays, geothermal energy with the heat of the center of the earth or even dams with hydraulic energy... but why do we never or almost never talk about marine energy? Or rather marine energies for that matter! Indeed, the oceans which cover - for the record - 70% of the planet, offer different technologies based on different forces of the marine environment to produce electricity: currents, tides but also swell for example. This is an incredible opportunity and we can see the possibility of a "blue revolution" in terms of energy. The reason why it is not discussed is probably because the exploitation of these oceanic forces is mainly at the experimental stage today and requires a long development.
Marine energies, what’s that?
Still little used today, marine energies could, once exploited on a large scale, provide low-cost energy all around the globe, without greenhouse gas emissions unlike so-called fossil fuels. They make it possible to produce electricity thanks to the intrinsic energy flows of the oceans through the movement of tides and currents, which represent a considerable force, or thermal energy which is based on the temperature differences between surface water and those of the depths.
Given the difficulties in implementing the current energy transition, marine energies represent significant potential and each have exponential margins for growth. Especially since, unlike sunshine or wind, the movement of tides and currents (the two most promising marine energies) is continuous and can be predicted in advance. While valuable in terms of this energy transition, renewable marine energies do not all have the same potential or the same level of development. Before they can be successful, they must reach technological and financial maturity because their costs are still too high to be profitable at this level of development.
Tidal energy or tidal power
Tides represent a gigantic and natural movement of water whose The ebb and flow can fill or empty reservoirs equipped with dams and turbines, without any other energy expenditure. These turbines, connected to a generator and an alternator, will produce electricity in real time which will be recovered by the adjoining tidal power plant where a transformer allows the alternating current to circulate in the high-voltage lines. In France, we have taken the lead in experimenting with this technology: EDF has been using this energy since 1966 in the Rance plant which produces 4% of the electricity consumed each year in Brittany.
Energy from ocean currents or hydroelectric energy
Here we use the kinetic energy of ocean currents that is captured by hydro turbines, the equivalent of wind turbines for wind. The currents, which are concentrated in certain areas near the coast, move the propellers whose rotation mechanically produces energy sent to an alternator that transforms it into electricity. The more ocean currents there are, the more energy can be produced. This is then conducted to dry land via submarine cables. The potential of this energy is interesting because most coasts around the world are subject to currents. It can therefore potentially be used anywhere. In France, EDF is experimenting with this technology with a demonstrator in the Côtes d'Armor whose viability must be tested both technically and economically. In Brittany, between the islands of Molène and Ouessant, a turbine ran for a year and produced electricity for the first time. Encouraging projects!
Wave energy or wave energy
It is different from current energy because it relies on the movement of waves, the result of wind blowing on the ocean surface. Indeed, when the wind blows on the ocean surface, its energy is transferred into the movements of waves or swells, which can travel long distances. Thus, we could recover, near the coast, the energy of the wind that has blown offshore and moved, but this technology is still in the testing phase.
Thermal energy
Thermal energy is based on the temperature difference between the bottom and the surface of the ocean. It offers the best results in waters where the differences are greatest between the bottom and the surface. In France, it is in Martinique that this new thermal energy is being tested via a floating electricity production platform, at the heart of the "Nemo" project.
Osmotic energy
Not yet exploited, the idea is to produce electricity from the pressure resulting from the chemical movement of molecules, triggered by the difference in salinity between fresh water and salt water, when they mix. When salt water and fresh water are poured side by side, separated by a permeable membrane, the fresh water naturally goes towards the salt water creating a pressure on the membrane that separates them: this is what can be exploited using a generator. This osmosis phenomenon has a very strong energy potential that could be used wherever waters mix: all estuaries and river mouths could be used, which offers a development perspective all over the world.
Marine energies thus represent a promising source of energy, which is just waiting to be exploited. France also has many assets to develop them thanks to its Normandy and Breton coasts, as well as its overseas territories. This perspective offers the vision of a real "blue revolution" in terms of energy transition, accompanied by strong economic, technological and human dynamism. We can indeed imagine the countless new professions, the development of industrial sectors, international trade and the opening of many markets. On condition that their development is supported and production costs are limited.
